The world's newest country tumbled back to the brink of civil war earlier this month. Heavy fighting in South Sudan's capital left hundreds dead. Tens of thousands of expatriates and refugees have fled the country with the help of foreign militaries, including that of the U.S. And the South Sudan government blames this return to violence on a miscommunication via Facebook. NPR's Gregory Warner explains.

GREGORY WARNER, BYLINE: Before I get to the Facebook post that allegedly sparked it all, I need to tell you just one piece of history about South Sudan. The president and the vice president are longtime enemies. They battled before the country's independence in 2011, and they waged war again in 2013. Last year, the two rivals finally agreed to work together towards peace. This was after endless rounds of peace talks involving western and African leaders. But the reconciliation was extremely short-lived.

President Salva Kiir and Vice President Riek Machar had only been 10 weeks together in office when each man's army started shooting at the other's. At least 287 people were killed and tens of thousands displaced.

South Sudan's ambassador to Kenya, Chol Ajongo, convened reporters in Nairobi to explain that the hostilities were triggered by a Facebook post, a post from the vice president's own press secretary.

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CHOL AJONGO: Misinforming his colleagues that the vice president, who was meeting with the president, was detained in the palace.

WARNER: He said this single post, claiming that President Kiir attempted to arrest Vice President Machar, that's what motivated Machar's army to storm the palace.

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AJONGO: And you can imagine if two armies are stationed in the capital city and fighting breaks out, you can imagine what can happen to the civil population.

WARNER: So let's just step back from these allegations for a second to ask, how is it that one country has two rival armies in the same capital city, two armies apparently ready to destroy each other for the sake of a status update?

JOHN PRENDERGAST: This is really a cookie-cutter approach to peacemaking in Africa.

WARNER: Human rights activist John Prendergast told me by Skype from Washington that he blames the way that the international peace deal was brokered. He said the two rival sides were brought together in a peace deal.

PRENDERGAST: And then they sign a deal. And somehow, there has to be a unified army created at the end of the rainbow.

WARNER: But neither of those armies trusts each other. And neither leader wants to relinquish power in oil-rich South Sudan. Prendergast says the West should have used economic sanctions to force both leaders to control their fighters.

PRENDERGAST: And we didn't do that. The international community didn't do it.

WARNER: And so, he says, the real cause of this outburst of violence was the lack of international pressure and not whatever Riek Machar's PR guy wrote on Facebook. By the way, Machar's team also disputes that the Facebook post triggered the battle. They say the president's forces started the fighting. Now the U.N. has called for both armies to leave the city. Secretary General Ban Ki-moon wants an arms embargo, and the African Union has voted to send in additional troops to buttress U.N. peacekeepers. Meanwhile, ordinary aid workers on the ground in South Sudan face a confusing patchwork of rival checkpoints and competing authorities.

DEEPMALA MAHLA: That is right.

WARNER: Deepmala Mahla is the South Sudan country director for Mercy Corps, which delivers aid across the country.

MAHLA: Who has authority in a particular area? It's quite interesting.

WARNER: If the terms of the peace deal was about bringing both leaders and both of their armies back to the country to reconcile, that's also meant a two-sided government, where each side monitors carefully how much aid is sent to the other. And that's why delivering aid to people whose lives were crushed by war is still so difficult in peacetime. Gregory Warner, NPR News, Nairobi. Transcript provided by NPR, Copyright NPR.